Orosomucoid (ORM) typing by isoelectric focusing: evidence for gene duplication of ORM1 and genetic polymorphism of ORM2

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Abstract
It has been demonstrated that the genetic polymorphism of human serum orosomucoid (ORM) is controlled by polymorphic ORM1 and monomorphic ORM2 loci. In this study a Japanese family was encountered in which several members had puzzling electrophoretic patterns consisting of four bands. The ORM patterns were due to the products of a duplicated ORM1 locus haplotype (ORM1 * 2·1) or the products of new variant alleles at the ORM2 locus. The ORM1 * 2·1 haplotype is very common in the Japanese population, occurring at an allele frequency of 0.16. The increased occurrence of ORM1 2-1 and the heterogeneity in band intensity among ORM1 2-1 phenotypes could be explained in terms of a duplicated gene ORM1 * 2·1. The ORM2 locus proved to be polymorphic, with six alleles in the Japanese population.